1. Field of the Invention
The present invention relates to a fuel injection device of an internal combustion engine.
2. Description of the Related Art
A fuel injection device designed to consecutively inject fuel two times from a fuel injector in one engine cycle of an internal combustion engine is disclosed in Japanese Unexamined Patent Publication (Kokai) No. 2000-18074. In more detail, in the fuel injection device described in this publication, so-called xe2x80x9cpilot injectionxe2x80x9d for injecting a small amount of fuel is performed immediately before the injection of fuel for driving the internal combustion engine.
When fuel is injected from a fuel injector, however, pulsation occurs in the fuel due to this fuel injection. If the fuel injector is communicated with a relatively large volume space such as a common rail, the pulsation arising due to the fuel injection will be transmitted to the common rail, reflected at the common rail, and again return to the fuel injector. If consecutively injecting fuel two times in one engine cycle as with the fuel injection device described in the above publication, the pulsation occurring due to the first fuel injection will return again to the fuel injector. Due to this, if the second fuel injection is performed while the fuel in the fuel injector is pulsating, the amount of fuel injection at the second fuel injection will end up deviating from the target amount.
An object of the present invention is to provide a fuel injection device which makes a fuel injector inject a target amount of fuel even if fuel in the fuel injector is pulsating.
To achieve this object, according to a first aspect of the invention, there is provided a fuel injection device provided with a fuel injector for injecting fuel to be fed into a combustion chamber of an internal combustion engine and a reservoir for temporarily storing fuel fed to the fuel injector, where fuel is injected at least two times in one engine cycle of the internal combustion engine, pulsation of fuel occurring in the fuel injector due to a prior injection comprised of a first fuel injection is transmitted to the reservoir, reflected at the reservoir, and returns to the fuel injector and, due to the effect of the returned pulsation, the fuel injection amount at a later injection comprised of a second fuel injection fluctuates, the fuel injection device of an internal combustion engine employing as parameters affecting the fuel injection amount at the later injection an opening timing of the fuel injector and an injection pressure of fuel from the fuel injector, estimating the amounts of fluctuation of the parameters at the later injection arising due to the pulsation, and controlling a control value relating to operation of the fuel injector based on the estimated amounts of fluctuation of the parameters at the later injection so that the target amount of fuel is injected from the fuel injector at the later injection.
In a second aspect of the invention, there is provided the first aspect of the invention, wherein the amounts of fluctuation of the parameters at the later injection represent the amount of fluctuation of the fuel injection amount at the later injection arising due to fluctuation in the parameters at the later injection, the amount of fluctuation of the fuel injection amount at the later injection arising due to fluctuation in the parameters at the later injection is estimated based on the estimated amounts of fluctuation of the parameters at the later injection, and a control value relating to operation of the fuel injector is controlled based on the estimated amount of fluctuation of the fuel injection amount at the later injection so that the target amount of fuel is injected from the fuel injector at the later injection.
In a third aspect of the invention, there is provided the first aspect of the invention, wherein a control value relating to operation of the fuel injector is controlled so that the fuel injection time at the later injection becomes a reference fuel injection time comprised of the fuel injection time in the case where the amount of fluctuation of the opening timing of the fuel injector at the later injection is zero.
In a fourth aspect of the invention, there is provided the first aspect of the invention, wherein a control value relating to operation of the fuel injector is controlled so that the opening timing of the fuel injector at the later injection becomes a reference opening timing comprising the opening timing in the case where the amount of fluctuation of the opening timing at the later injection is zero.
In a fifth aspect of the invention, there is provided the fourth aspect of the invention, wherein the amounts of fluctuation of the parameters at the later injection are calculated from functions having as variables the interval time comprised of the time from the prior injection to the later injection and, when a control value relating to operation of the fuel injector is controlled so that the opening timing at the later injection becomes the reference opening timing, the interval time used for estimating the amount of fluctuation of the fuel injection pressure at the later injection is calculated assuming that the fuel injector opens at the reference opening timing.
In a sixth aspect of the invention, there is provided the third aspect of the invention, wherein a control value relating to operation of the fuel injector is controlled so that a closing timing of the fuel injector at the later injection becomes a closing timing having the fuel injection time at the later injection as the reference fuel injection time.
In a seventh aspect of the invention, there is provided the first aspect of the invention, wherein an opening speed of the fuel injector is employed in addition to the above parameters.
In an eighth aspect of the invention, there is provided the first aspect of the invention, wherein when the fuel injection time at the later injection is shorter than a predetermined time, only the opening timing of the fuel injector is employed as a parameter.
In a ninth aspect of the invention, there is provided the first aspect of the invention, wherein the fuel injector has at least one injection hole for injecting fuel, a needle valve moving reciprocally inside the fuel injector and closing the injection hole, a first chamber storing fuel applying pressure to a wall surface of the needle valve at the injection hole side and to be injected from the injection hole, and a second chamber positioned at an opposite side to the first chamber relative to the needle valve and storing fuel, and the amount of fluctuation of the opening timing at the later injection is estimated based on a time-differentiated value of pressure of the fuel in the first chamber.
In a 10th aspect of the invention, there is provided the first aspect of the invention, wherein a relationships between amounts of fluctuation of the parameters at the later injection and the interval time when fixing conditions other than the interval time comprised of the time from the prior injection to the later injection are found in advance, and the amounts of fluctuation of the parameters at the later injection are estimated from the interval time based on the relationships.
In an 11th aspect of the invention, there is provided the 10th aspect of the invention, wherein the amounts of fluctuation of the parameters at the later injection differ according to the fuel injection time in the prior injection, the fuel injection time in the prior injection is employed as the condition other than the interval time, the relationships between the amounts of fluctuation of the parameters at the later injection and the interval time are found for the fuel injection time in the prior injection serving as a reference, and the amounts of fluctuation of the parameters at the later injection estimated based on the relationships are corrected in accordance with the fuel injection time at that time in the prior injection.
In a 12th aspect of the invention, there is provided the 10th aspect of the invention, wherein the amounts of fluctuation of the parameters at the later injection differ according to the fuel injection time at the later injection, the fuel injection time at the later injection is employed as the condition other than the interval time, the relationships between the amounts of fluctuation of the parameters at the later injection and the interval time are found for the fuel injection time at the later injection serving as a reference, and the amounts of fluctuation of the parameters at the later injection estimated based on the relationships are corrected in accordance with the fuel injection time at that time at the later injection.
In a 13th aspect of the invention, there is provided the 10th aspect of the invention, wherein the amounts of fluctuation of the parameters at the later injection differ according to at least one of an average pressure of the fuel and a temperature of the fuel, at least one of the average pressure of the fuel and the temperature of the fuel is employed as the condition other than the interval time, the relationships between the amounts of fluctuation of the parameters at the later injection and the interval time are found for the average pressure of the fuel serving as a reference and the temperature of the fuel serving as a reference, and the amounts of fluctuation of the parameters at the later injection estimated based on the relationships are corrected in accordance with at least one of the average pressure of the fuel at that time and the temperature of the fuel at that time.
In a 14th aspect of the invention, there is provided the 10th aspect of the invention, wherein the amounts of fluctuation of the parameters at the later injection differ according to the pulsation propagation speed in the fuel, the pulsation propagation speed in the fuel is employed as the condition other than the interval time, the relationships between the amounts of fluctuation of the parameters at the later injection and the interval time are found for the pulsation propagation speed in the fuel serving as a reference, and the amounts of fluctuation of the parameters at the later injection estimated based on the relationships are corrected in accordance with the pulsation propagation speed in the fuel at that time.
In a 15th aspect of the invention, there is provided the 14th aspect of the invention, wherein the amounts of fluctuation of the parameters at the later injection estimated based on the above relationships are corrected so that the faster the pulsation propagation speed in the fuel at that time, the shorter the interval time the amounts of fluctuation correspond to.
In a 16th aspect of the invention, there is provided the 14th aspect of the invention, wherein the pulsation propagation speed in the fuel is calculated from a function having at least one of the average pressure of the fuel and the temperature of the fuel as a variable.
In a 17th aspect of the invention, there is provided the 14th aspect of the invention, wherein the device is provided with a pressure sensor for detecting a pressure of the fuel and a change in pressure of the fuel found from an output value of the pressure sensor is used to calculate the pulsation propagation speed in the fuel.
In an 18th aspect of the invention, there is provided the 17th aspect of the invention, wherein the propagation speed is calculated when a predetermined condition stands.
In a 19th aspect of the invention, there is provided the 18th aspect of the invention, wherein the predetermined condition is that an extent of change of the average pressure of the fuel is smaller than a predetermined extent.
In a 20th aspect of the invention, there is provided the 18th aspect of the invention, wherein the predetermined condition is that the average pressure of the fuel is a predetermined pressure and the predetermined pressure includes a plurality of values.
In a 21st aspect of the invention, there is provided the 18th aspect of the invention, wherein a pulsation propagation speed in the fuel when the temperature of the fuel is a predetermined reference temperature and the average pressure of the fuel is a predetermined reference pressure is stored in advance as a reference propagation speed, the predetermined condition is that the temperature of the fuel is the reference temperature and the average pressure of the fuel is the reference pressure, and the propagation speed calculated when the predetermined condition stands is made the reference propagation speed.
In a 22nd aspect of the invention, there is provided the 17th aspect of the invention, wherein the device is provided with a plurality of fuel injectors, fuel is fed to these fuel injectors from the reservoir, and the pulsation propagation speed in the fuel is calculated for the fuel injector at the location furthest from the pressure sensor.
In a 23rd aspect of the invention, there is provided the 10th aspect of the invention, wherein the amounts of fluctuation of the parameters at the later injection differ in accordance with the average pressure of the fuel, the average pressure of the fuel is employed as the condition other than the interval time, the relationships between the amounts of fluctuation of the parameters at the later injection and the interval time are found for the average pressure of the fuel serving as a reference, the estimated amounts of fluctuation of the parameters at the later injection are corrected so that the amount of fluctuation of the fuel injection amount at the later injection becomes larger in a plus direction when the average pressure of the fuel at that time is higher than the average pressure of the fuel serving as a reference, and the estimated amounts of fluctuation of the parameters at the later injection are corrected so that the amount of fluctuation of the fuel injection amount at the later injection becomes larger in a minus direction when the average pressure of the fuel at that time is lower than the average pressure of the fuel serving as a reference.
In a 24th aspect of the invention, there is provided the first aspect of the invention, wherein fuel is injected at least three times in one engine cycle of the internal combustion engine, and the total of the amounts of fluctuation of the parameters in the third fuel injection arising due to pulsation occurring due to the first fuel injection and the amounts of fluctuation of the parameters in the third fuel injection arising due to pulsation occurring due to the second fuel injection are made the amounts of fluctuation of the parameters in the third fuel injection.